Hospital beds are well known in the art. Certain beds have been adapted to assist a patient to a vertical or standing position from a horizontal position when the patient is lying on the bed. This may be particularly useful for patients who have had surgery that makes movement more difficult, such as knee surgery, or for patients who have other health conditions that may make getting out of bed difficult, such as a severely obese person. Existing beds that assist a patient to a standing position often require the patient to be moved so that their feet contact a support surface of the bed that the patient will be standing on when the bed lifts them into a standing position. However, as many of these patients have limited mobility, this may be difficult to accomplish. Additionally, patients who do not leave bed very often may develop sores form being moved on the bed in order to position the patient's feet in contact with the support surface. Further, patients often need to be repositioned in bed from the foot of the bed toward the head of the bed, and moving the patients is extremely difficult and physically demanding on care givers. Therefore, a need exists for a bed that positionable to assist a patient to a standing position that does not require the patient to be moved relative to a mattress on the bed, and for a bed having a positionable mattress to assist the care giver in relocating the patient lengthwise on the bed. The present invention seeks to overcome certain of these limitations and other drawbacks of the prior art, and to provide new features not heretofore available. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings